In the pharmaceutical industry, parenteral drugs, such as drugs intended for intravenous or intramuscular injection, are typically packaged in small glass vials, Crimp-top vials are used for injectibles. Small glass ampoules may be used for packaging single doses of hypodermic medicines. Glass vial sizes are typically in a range of 1 to 1,000 ml and may be of molded or tubular varieties.
For years, pharmaceutical manufacturers have lost millions of dollars worth of parenteral drugs through destructive testing intended to verify correct fill volume from their automatic vial filling equipment. Such waste gives rise to opportunity for increased yield and profitability where a non-destructive alternative can be found. Thus, what it is needed is a way to accurately measure liquid volume inside a sealed, glass vial without removing its contents or otherwise violating its salability.
Automatic filling machines are found in most high volume, parenteral drug packaging operations. They use microprocessor-based controls and precision components to accurately package liquid pharmaceuticals at rates of 300 vials per minute on a single filling line. For an industry that demands exacting quality control, filling machines offer consistent, economical operation unmatched by manual alternatives.
Because filling machines contain and interact with time-varying elements, they must include closed-loop control systems to maintain consistent fill volume. Control feedback is typically received from volume measurements performed on vials that have recently been filled. When volume measurements reveal deviation from the target volume, corrective action is taken hopefully before product specifications are violated. On the other hand, if volume measurements reveal fill volumes outside of predetermined tolerance, all of the incorrectly filled or even suspect vials generally are destroyed.
Many existing filling lines do not measure fill volume automatically. Instead, it is common practice to manually select a vial from each fill nozzle, periodically, for example every few minutes, remove its contents and measure them by gravimetric or volumetric means. Because a liquid is removed from the vial before measurement, this method almost always results in product destruction.
For most of today's drugs the economic impact to the producer is significant. Destructive testing costs range from a few hundred to a few thousand dollars each week depending on product value. With the emergence of increasingly expensive drugs and the escalating pressure on the industry to lower prices, the need is increasingly important to gain competitive advantage through non-destructive measurement techniques.